In the continuous casting of metals, in particular, steel or aluminum, introduction of flowing molten metal into a mold cavity requires precise control to avoid detrimental effects on the quality of the cast product. Variables such as quantity of metal introduced in the mold cavity, distribution of molten metal during the pouring sequence, heat loss and oxidation rates all affect product quality.
In order to provide acceptable levels of quality in cast products, pouring tubes or downspouts have been developed to introduce molten metal in a submerged manner.
Submerged-type continuous casting nozzles or downspouts typically include passageways on the distal end thereof to direct flow of molten metal in a particular direction. U.S. Pat. No. 3,996,994 to Schrewe et al. discloses a feeder pipe for a mold for continuous casting of steel which has a near-rectangular inner and outer contour with oppositely directed discharge ports for feeding toward the small sides of a mold.
U.S. Pat. No. 4,993,608 to Thorner discloses a pouring tube for the introduction of a metallic melt into a strip-casting mold which includes a plurality of vertically aligned slots arranged near the distal end of the pouring tube.
U.S. Pat. Nos. 4,671,433 to Podrini et al. and 4,858,794 to Sugiura et al. disclose submerged nozzles for continuous casting which include angled discharge ports located at the nozzle tip.
U.S. Pat. No. 4,487,251 to Cahoon et al. discloses a nozzle for a continuous casting apparatus which includes facilities for passing a fluid medium, e.g. argon, through its wall members transverse to the direction of molten metal flow to retard accumulation of undesirable formations such as metal oxides.
U.S. Pat. No. 4,819,840 to Lax et al. discloses a refractory submerged pouring nozzle having a bottom plate and two opposing outflow orifices. Each outflow orifice has a roof-shaped guide element projecting outwardly. The nozzle also includes a vertex and guide surface on the bottom plate thereof.
Downspouts are also employed in direct chill or electromagnetic continuous casting of aluminum alloys. However, continuous casting of aluminum alloys is sensitive to excessive contact with the atmosphere caused by turbulence and/or splashing during pouring of molten aluminum using a downspout. This excessive contact results in the formation of oxides of the molten metal which float to the top of the molten metal or remain in the ingots as impurities. Excessive oxides on the top of the molten metal require complicated ingot head skimmers and mechanical skim dams. Impurities remaining in the ingot require extensive conditioning work such as scalping to prepare the ingot surface for further working operations.
In response to the deficiencies in downspout designs in these types of continuous casting processes, channel bags are utilized in conjunction with a downspout to minimize turbulence during the casting process. With reference now to FIG. 1, a downspout in combination with a channel bag is generally designated by the reference numeral 100 and seen to include a downspout 101 extending below the surface 105 of molten metal that is being solidified to form an ingot 103 being cast. The channel bag 107 is configured to direct flow of the molten metal, as indicated by the arrows within the chamber created by the channel bag 107, toward the small sides 109 of the ingot 103.
Although channel bags assist in specific distribution of the molten metal during continuous casting, several drawbacks exist when utilizing channel bags during casting. During start-up operations of the continuous casting, the channel bags may stick to the starter block. During casting of high magnesium content aluminum alloys, the channel bags may clog which obstructs flow of molten metal into the ingot. Furthermore, oxides formed on the top surface of the molten metal in the mold cavity may periodically release through the sides of the channel bag and accumulate on the long face of the ingot causing cracking or other surface defects.
In view of the disadvantages associated with channel bags, a need has developed to improve molten metal distribution, reduce turbulence and eliminate the drawbacks associated with channel bags in continuous casting processes, especially direct chill or electromagnetic continuous casting of aluminum alloys.
In response to this need, the present invention provides a flow-vectored downspout for continuous casting which includes a flow diffuser arranged at the distal end of a downspout. The flow diffuser includes a series of slots configured in a particular manner and specially configured bottom plate to vector molten metal flow to all vital areas of the ingot head while reducing turbulence and eliminating the need for a channel bag during casting.